Final answer:
Hypothermia does not lead to an increase in PETCO2; instead, hypothermia may cause a decrease in PETCO2 due to a reduced metabolic rate, whereas hypercapnia results from conditions that impair ventilation and currently results in increased PETCO2.
Step-by-step explanation:
The conditions in which the partial pressure of end-tidal CO2 (PETCO2) is increased include enhanced metabolic activity, impaired respiratory functions, and any condition resulting in hypoventilation. Among the options provided, hypothermia is the one that does not generally lead to an increase in PETCO2; instead, it may decrease due to a reduced metabolic rate.
Conditions such as hyperventilation, fever, or increased exercise lead to an increased rate and depth of ventilation, known as hyperpnea, which maintains normal blood oxygen and carbon dioxide levels. However, in scenarios where there is impaired ventilation (not matching the metabolic demand), such as with certain drug use or respiratory diseases, hypercapnia occurs, leading to increased PETCO2. Apnea, a cessation of breathing, would not result in increased PETCO2 as it stops the production of CO2.